JPH0342812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention uses a pulse input processing method, particularly in a digital processing device such as a microcomputer, by counting the number of pulse inputs per unit time. The present invention is a system for measuring rotational speed, etc., and relates to a pulse input processing method that reduces the burden on hardware and software and can flexibly deal with required resolution, etc.

[Conventional technology and problems]

For example, by inputting pulses from a rotation sensor such as the rotation speed of a motor or a car engine,
Measurement is performed using a microcomputer.

FIG. 5 shows an example of a conventional method in which pulses are counted using an interrupt, and FIG. 6 shows an example of a conventional method in which pulses are counted using a hardware counter.

For example, pulse input is 0 to 255pps (pulse/sec)
Assume that the number of pulses per second is measured under the condition that the resolution is 1 pps. Fifth
In the method shown in the figure, the pulse input to be measured is passed through a pulse shaping circuit 1 to a microprocessor 2.
is applied to interrupt terminal 3 of In the interrupt processing of the microprocessor 2, the value of the internal counter is incremented by 1 for each interrupt, and the contents of the internal counter are read every 1 second of unit time. According to this method, the hardware is simple, but the maximum
There is a problem that 255 interrupt processing is required, resulting in a large overhead. Furthermore, if another interrupt process with a high priority is being executed, there is a problem in that the timing of counting is delayed.

On the other hand, in the system using the 8-bit counter 4 shown in FIG. 6, the number of pulse inputs is automatically counted by the counter 4, so the microprocessor 2 simply reads the output Q ₀ of the counter 4 every second. ~ Just read Q ₇ . However, in this method,
A counter with a bit width corresponding to the maximum number of input pulses per unit time is required, which increases the burden on the hardware. Additionally, changes in resolution conditions, measurement unit time, maximum number of input pulses, etc.
Since this is limited by the counting capacity of the counter 4, there is a problem in that it may not be possible to deal with it flexibly.

[Means for solving problems]

The present invention aims to solve the above problems, and reduces software overhead by measuring pulse input with a counter smaller than the maximum number of input pulses per unit time and compensating for counter overflow with an internal register. It also provides a versatile measurement method. That is, the pulse input processing method of the present invention is a counter that counts pulses to be measured in a pulse input processing method that measures the number of input pulses per unit time in a digital processing device, and whose maximum counting range is within a unit time. The digital processing device includes a counting circuit smaller than the maximum number of input pulses per hit, and the digital processing device inputs the output of the counting circuit in a time period that does not exceed the counting range of the counting circuit, and inputs the output of the counting circuit in the previous period. An overflow counter that detects the presence or absence of an overflow by comparing the magnitude with a value, and counts the number of overflows of the counting circuit, and a number of overflows counted by the overflow counter and the input value of the counting circuit The present invention is characterized by comprising a pulse number calculation section that calculates the number of input pulses per unit time for each unit time based on the pulse number calculation unit. Hereinafter, embodiments will be described with reference to the drawings.

〔Example〕

FIG. 1 is a block diagram of the configuration of an embodiment of the present invention, FIG. 2 is a diagram explaining the processing of the overflow counting section shown in FIG. 1, FIG. 3 is a diagram explaining the processing of the pulse number calculation section shown in FIG. 1, and FIG. shows another embodiment of the present invention.

In FIG. 1, 1 is a pulse shaping circuit, 10 is a 4-bit counter, 11 is a digital processing device consisting of a microprocessor and memory, and 12 is a 4-bit counter.
is an input register; 13 is an overflow counter that inputs the value of the counter 10 and counts the number of overflows when an overflow occurs; 14 is a previous cycle counter value storage unit that stores the counter value input in the previous cycle; 15 is an overflow number storage unit for counting the number of overflows; 16
17 is a total pulse number storage unit used to calculate the total number of pulses; 18 is a pulse number calculation unit that calculates the number of pulses per unit time; 19
is a result register in which the calculated number of pulses is stored,
20 represents a timer that measures a predetermined time.

With the circuit configuration shown in FIG. 1, the pulse input ranges from 0 to
The number of pulses per second is measured at 255 pps (pulse/sec) and the resolution is 1 pps.

In the case of the present invention, the measurement range of the counter 10 does not necessarily have to be larger than the maximum number of input pulses per unit time. In this example, counter 10
is 4 bits, and the counting range is 0 to 15.
Therefore, at a maximum input of 255 pps, t = 15/255 = approximately 0.059 (sec), and there is a possibility that the counting range will be exceeded at a minimum of 0.059 sec. Therefore, the overflow counting section 13
The time (t=
The timer 20 is activated at intervals shorter than 0.059 sec, for example, every 1/20 sec.
Then, the overflow counting section 13, for example,
Process as shown. Note that the overflow counting section 13 may be activated using other activation means, such as a software timer, instead of using a timer interrupt.

When the overflow counting section 13 is activated every 1/20 seconds, it first inputs the value of the counter 10 to the input register 12 through the process 30 shown in FIG. Then, as a result of the determination in process 31, the value x is compared in magnitude with the counter value y stored in the previous cycle counter value storage unit 14 and read 1/20 seconds ago.
If the value x is greater than or equal to the previous value y, control is transferred to process 33 and the value x of the input register 12 is transferred to the previous cycle counter value storage section 14.
As a result of the determination in process 31, if the value x is smaller than the previous value y, it means that the counter 10 is overflowing. Therefore, in this case, process 32
Accordingly, the overflow count z stored in the overflow count storage unit 15 is updated by +1, and the process moves to process 33. Note that the cycle at which the overflow counter 13 is activated is 1/20 (0.05) sec, which is smaller than the minimum counting range time of the counter 10, 0.059 sec, so the counter 10 is activated twice or more during that cycle. There will be no overflow.

The pulse number calculation unit 18 is activated, for example, by the timer 20 every 1 second of measurement unit time. The pulse number calculation unit 18 calculates the number of input pulses per unit time by performing the processing as shown in FIG. That is, first, the second
1/ similar to processes 30 to 33 shown in the figure.
Processing is executed every 20 seconds. Note that this process 34
The overflow counter 1 is used instead of independently.
3 may be called and executed. Next, in step 35, the total number of pulses a including overflow is determined.

a=16*z+y The previous total pulse number storage unit 16 stores the total number of pulses b from 1 second ago, and the current number of pulses c from 1 second is calculated by the process 36 as c=a-b. , are stored in the result register 19. Finally, in step 37, the number of pulses a is set in the previous total pulse number storage section 16 and the number of pulses b is updated for the next processing.

For example, if a 3-bit counter is used instead of the 4-bit counter 10 under the same measurement conditions, the measurement range is 0 to 7.
Since the time during which overflow may occur only once is t=7/255=approximately 0.027 (sec), the cycle for starting the overflow counter 13 may be set to 0.027 sec or less.

Further, when using a 5-bit counter, for example, overflow processing may be similarly executed at a cycle of 0.12 seconds or less. When pulse input is counted directly by interrupt processing, the counting processing must be performed up to 255 times per second, that is, at an average interval of about 4 msec, so the processing load is significantly reduced compared to that case. That will happen. Also, even if the maximum number of input pulses changes,
This can be easily handled by simply changing the overflow processing cycle.

FIG. 4 shows another embodiment of the invention. In the case of the example shown in FIG. 4, instead of starting the overflow counting section 13 and the pulse number calculating section 18 separately, only the overflow counting section 13 is started every 1/20 seconds by the timer 20. . After executing processes 30 to 33 shown in FIG. 2, the overflow counting unit 13 increments the value d of a startup counter (not shown) by 1, and when the value d reaches 20, clears the counter value. Then, the pulse number calculation unit 18 is activated. In this case as well, the number of pulses per unit time is determined in the same way.

For example, when the present invention is applied to detecting the rotation speed of an automobile engine, the rotation sensor outputs 25 pulses for one rotation of the automobile engine. For example, if the measurement unit time is 60 msec, the overflow processing period is 6 msec, and the pulse counter is 4
If you use bits, the unit time is 60m.
The maximum number of input pulses that can be counted per sec is (15/0.006) * 0.06 = 150 (pulse), which is approximately 2500 pulses per second. Therefore,
In this example, it is possible to measure approximately 100 revolutions per second, and a maximum of approximately 6000 rpm (revolutions per minute) for one minute.

〔Effect of the invention〕

As described above, according to the present invention, measurement over a large counting range can be realized with a counter having a relatively small number of stages. Furthermore, since the processing cycle can be made longer and the processing can be performed at a constant cycle, other main processing in the digital processing device that performs counting will not be overwhelmed. By changing the number of stages of the counter, it is possible to set the hardware load and the software load with an arbitrary balance, and even when the maximum number of input pulses is changed, it becomes possible to easily deal with the change.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the configuration of an embodiment of the present invention, FIG. 2 is a diagram explaining the processing of the overflow counting section shown in FIG. 1, FIG. 3 is a diagram explaining the processing of the pulse number calculation section shown in FIG. 1, and FIG. shows another embodiment of the present invention, FIG. 5 shows an example of a conventional system in which pulses are counted using an interrupt, and FIG. 6 shows an example of a conventional system in which pulses are counted using a hardware counter. In the figure, 1 is a pulse shaping circuit, 10 is a counter,
Reference numeral 11 represents a digital processing device, 13 represents an overflow counter, and 18 represents a pulse number calculation unit.

Claims (1)

[Scope of Claims] 1. In a pulse input processing method that measures the number of input pulses per unit time in a digital processing device, a counter that counts pulses to be measured and whose maximum counting range corresponds to the maximum input pulse per unit time. The digital processing device is equipped with a counting circuit smaller than the number of pulses, and the digital processing device inputs the output of the counting circuit in a time period that does not exceed the counting range of the counting circuit, and calculates the magnitude of the output from the counting circuit that is smaller than the value input in the previous period. an overflow counter that detects the presence or absence of an overflow and counts the number of overflows of the counting circuit; and a unit time based on the number of overflows counted by the overflow counter and the input value of the counting circuit. 1. A pulse input processing method, comprising: a pulse number calculation unit that calculates the number of input pulses per unit time for each input pulse.